German patent application P 40 40 855.8 (Le A 27 877) describes a process for isolating polymers from their solvents by addition of fluids containing carbon dioxide at temperatures of 30.degree. C. to 280.degree. C. and under pressures of 1 bar to 1,000 bar, characterized in that the concentration of the polymers in their solvents is between 5% by weight and 80% by weight and in that the fluid containing carbon dioxide consists of at least 50% by weight carbon dioxide.
Compared with other processes for isolating polymers from their solvents, as described for example in U.S. Pat. No. 4,634,761, EP 334 314 A2, DE 3 840 293 A1, JP 01 16 8730-A2 and the publication "Yamamoto Koji" et al.: Kagaku Kogaku Ronbunshu 15 (3), Vol. 1989, pages 673-675, the process described in the German patent application has the advantage that large quantities of solvent are removed quickly and easily without significant exposure of the product to heat.
It has now been found that the isolation process described in German patent application P 40 40 855.8 (Le A 27 877) can be improved in regard to the production of polycarbonate in powder form.